I'm starting something called "Study Week" (SW) for my own learning purposes. In the past week, I've drawn simple thumbnails of abstract shapes and rendered them — the results are better than expected! There's a unique quality in starting with abstract forms because happy accidents occur quite often.
The first two images show the process of transformation through building forms using lighting to emphasize certain features of the designs. The top row far left design feels more like a typical Bruce Wayne aka Batman type of vehicle. The other designs are more abstract and unique in its own way. I might further develop a select few.
The process for the "Wayne Enterprises concepts" includes: fine liner hand drawings, SketchBookPro rendering, Photoshop final touches and layout.
The final part of this SW was all fine liner thumbnail drawings, each ranging approx. 1 minute to do. These were meant to be quick brainstorming thumbnails to jumpstart my creativity before I started the spacecraft concept renderings.